1. Field of the Invention
The present invention relates to a graphing method for presenting values associated with two data sets, in which processing of zero and negative denominator values is possible, and angle transformation is performed prior to plotting on a graph such that graph compression is not required. The present invention also relates to a graphing apparatus and a computer program product that stores a program for executing the graphing method.
2. Description of the Related Art
It is often desirable to compare two data sets. One way to accomplish this is to calculate ratios in which the denominator is a function of a value from the first data set and the numerator is a function of at least a corresponding value from the second data set. For example, a value of a present period may be divided by a corresponding value of a previous period and the resulting quotient multiplied by 100% to thereby obtain what is referred to herein as a completion rate. As another example, a value of the previous period may be subtracted from a corresponding value of the present period, the resulting difference divided by the value of the previous period, and this resulting quotient multiplied by 100% to thereby obtain what is referred to herein as a growth rate.
However, when the denominator is zero, it is neither possible to calculate the completion rate nor the growth rate. Such values may appear as NA (not available) when presented in a table, or may appear as breaks or empty spaces when presented on a graph.
Furthermore, when the denominator used in calculating the completion rate or the growth rate is small, the resulting completion rate or growth rate is a very large value. One consequence of this is that the graph may need to be compressed so that all values appear on the graph. However, this may make it impossible to discern variations in the completion rates or growth rates that are not large. One conventional way in which this problem is dealt with involves the use of logarithms. While a marked improvement in this regard is realized with the use of logarithms, it is not possible to obtain the log of zero and negative values. Such points are unable to be presented on the graph.